Heat treating apparatus

ABSTRACT

Apparatus for heat-treating articles including a rotatable ring having a plurality of article-receiving pockets disposed about its periphery and an inductive heating coil adjacent the ring. As the ring is rotated articles in the pockets are carried in succession past the coil and are heated. The apparatus also includes means for ejecting an article from the ring including an air supply, a conduit through which air under pressure from the supply may be directed against an article to dislodge it from the ring, and a normally-closed valve in the conduit inhibiting air flow through the conduit. A photocell adjacent the coil is responsive to changes in radiation emitted by each article as it is heated. The photocell is operable to detect when an article carried by the ring has been heated to a preselected temperature and when it detects such is operable to open the valve of the ejecting means to eject the heated article from the ring.

United States Patent 1 Potter HEAT TREATING APPARATUS [75] Inventor: Harold F. Potter, Aurora, Oreg.

[73] Assignee: Carlton Company, Portland, Oreg.

[22] Filed: Nov. 1, 1971 211 Appl No; 194,657

[52] US. Cl 2l9/l0.69, 219/1075, 221/13,

221/150 H, 266/5 E [51] Int. Cl. H0511 5/02 [58] Field of Search 263/6, 7; 219/1069,

219/1049, 10.41, 10.43, 10.75, 10.77, 10.79, 10.67, 10.71, 10.73, 501, 502; 266/4 E, 5 E, 4 S; 307/117; 221/150 H, 13, 278

[56] References Cited UNITED STATES PATENTS 3,005,894 10/1971 Carbo et al. 2l9/10.69 3,435,173 3/1969 Connoy et al. 219/502 X 3,674,141 7/1972 Abraham et al. 221/278 2,942,089 6/1960 Baker et a]. 2l9/10.69 3,245,509 4/1966 Larson 307/117 X 3,552,645 111971 Boyd 219/502 2,840,678 6/1958 Hill et a1. 219110.69 2,907,858 10/1959 Distler 219/1069 July 24, 1973 2,476,935 7/1949 Wharfl' 219/1069 Primary Examiner-J. V. Truhe Attorney-M. H. Hartwell, Jr.

[5 7 ABSTRACT Apparatus for heat-treating articles including a rotatable ring having a plurality of article-receiving pockets disposed about its periphery and an inductive heating coil adjacent the ring. As the ring is rotated articles in the pockets are carried in succession past the coil and are heated. The apparatus also includes means for ejecting an article from the ring including an air supply, a conduit through which air under pressure from the supply may be directed against an article to dislodge it from the ring, and a normally-closed valve in the conduit inhibiting air flow through the conduit. A photocell adjacent the coil is responsive to changes in radiation emitted by each article as it is heated. The photocell is operable to detect when an article carried by the ring has been heated to a preselected temperature and when it detects such is operable to open the valve of the ejecting means to eject the heated article from the ring.

10 Claims, 6 Drawing Figures PATENIEU JUL 2 4191s SHEEI 1 BF 2 HEAT TREATING APPARATUS This invention relates to apparatus for heat-treating articles.

In the heat-treating of articles, and especially small articles, it is desirable to be able to heat them very rapidly, to achieve high production rates. Along with mass production, it is desirable, and in many cases imperative, to assure that each individual part is heated to its proper temperature. In the past, devices have been designed for mass producing heat-treated articles, however, many of these have been too slow and have govcrned the temperature rise in the article only by holding it adjacent a heater for a preselected time interval. Such previous devices generally have not had the capability of checking the temperature of each individual article as it is heated and removing it from the heater when it reaches the proper temperature. Previous devices, therefore, often produced articles which were underheated or overheated. Further, when heattreating parts, it is often desirable to heat-treat only a localized portion of each article.

A general object of the instant invention is to provide novel apparatus for heat-treating articles which operates in a simple and efficient manner to overcome the disadvantages and problems of previous apparatus as described above.

More specifically, an object of the invention is to provide novel apparatus for heat-treating articles which apparatus is operable to convey articles in succession to a heating region, supply heat thereto, detect when each article has been heated to a preselected temperature, and remove each article from the heating area when it reaches such preselected temperature.

Yet another object of the invention is to provide novel heat-treating apparatus which includes a conductive conveyor element having pockets therein for receiving articles to be heat-treated and an inductive coil past which the element and articles pass operable to produce inductive heating of the articles. The pockets in the conveyor element may be so formed that heating of the element occurs in a selected localized region of the article. I

In a specific embodiment of the invention, the conveyor element is aring having article-receiving pockets defined about its periphery, which pockets are shaped to loosely receive individual articles to be heated. Each article is held in its respective pocket by a magnet adjacent the ring, and the ring is rotated, whereby the articles are moved in succession into an area adjacent an inductive heating coil. As the ring rotates, each article is heated on passing adjacent the coil and a photocell adjacent the ring detects when each article is heated to a preselected temperature. When the photocell detects that an article has reached such preselected temperature, it causes a stream of fluid under pressure to be directed against one side of such article to dislodge it from the ring, whereby it may drop into a quenching medium.

These and other objects and advantages will become more fully apparent as the following description is read in conjunction with the drawings, wherein:

FIG. 1 is a perspective view of apparatus for heattreating articles constructed according to an embodiment of the invention;

FIG. 2 is a perspective view of a modified form of means for supplying articles to the heat-treating apparatus;

FIG. 3 is an enlarged cross-sectional view taken generally along the line 3-3 in FIG. 1;

FIG. 4 is a view taken along the line 4-4 in FIG. 3;

FIG. 5 is a simplified schematic drawing of sensing and ejecting means in the apparatus; and

FIG. 6 is an enlarged cross-sectional view taken generally along the line 6-6 in FIG. 1.

Referring now to the drawings, and first specifically to FIG. 1, at 10 is indicated generally apparatus according to the invention. The apparatus includes a motor and control housing 12 on which is mounted a heating wheel 16. Wheel 16, which is also referred to herein as conveying means, is connected to a motor in housing 12 and is mounted for powered rotation about a horizontal axis in the direction of arrow 18.

Describing wheel 16 in detail, it includes a circular backing member 22 constructed of a nonconductive acrylic material. Backing member 22 has a rim portion 22a and a hub portion 22b. The periphery of the hub define an annular shoulder 22c (see FIG. 3). An annular groove 26 formed in shoulder 220, seen in cross section in FIG. 3, extends circumferentially about hub portion 22b.

The heating wheel also includes an annular ring, or band, element 30, constructed of an electrically conductive material, such as copper. The ring has an inner diameter corresponding to the outer diameter of shoulder 220 of the hub and a width greater than the width of the shoulder. The ring is secured to hub 22b with a portion of the ring overlying the shoulder and another portion projecting outwardly therefrom (see FIG. 3).

Ring has a plurality of article-receiving pockets 34 defined about its periphery in that portion of the ring which overlies shoulder 220. The pockets are substantially in line about the circumference of the wheel, overlie groove 26 in the hub, and are spaced from each other as is best seen in FIG. 1. The pockets are constructed to receive and hold a specific type of part to be heated. In the embodiment illustrated, and referring specifically to FIG. 3, the pockets are constructed to receive and hold pivot pins, or rivets, 38 such as may be used to interconnect the links in a power saw chain. Such a pin has a circular rim 38a and cylindrical hubs 38b, 38c extending outwardly in opposite directions from the rim. Pocket 34 has a substantially cylindrical receiving portion 340 and a guide portion 34b. The receiving portion has a diameter which is slightly greater than the diameter of rim 38a of the pin and a thickness substantially equal to the thickness of the rim. Guide portion 34b of pocket 34 has an outer diameter which is greater than the diameter of receiving portion 34a and has concave, or dished, sides which curve inwardly toward, and intersect, the cylindrical sides of portion 34a.

Referring still to FIGS. 3 and 4, each pocket 34 has an elongated slot 40 associated therewith which extend fully through ring 30 and advances from the pocket laterally of the ring. Slot 40 terminates at its left end at a point spaced inwardly from the left edge of ring 30, as seen in FIGS. 3 and 4, and terminates at its right end at the outer edge of guide portion 34b of the pocket. A much narrower slot 42 extends between and interconnects slot 40 and the receiving portion 34a of pocket 34.

A conduit 46 defined in ring 50 meanders between and around pockets 34 and slots 40. This conduit is adapted to direct a flow of coolant fluid therethrough to cool the heating wheel during operation. Means for supplying coolant fluid to the conduit is indicated generally at 48 in FIG. 1. Supply means 48 includes a pair of coolant fluid supply and exhaust tubes 50, 52. Tube 50 is adapted to supply pressurized coolant fluid from a suitable source through a conventional rotatable coupling, indicated generally at 54, to a supply tube 56. Tube 56 is connected through a channel (not shown) in backing member 22 to one end of coolant fluid conduit 46. The other end of conduit 46 is connected through a suitable channel (not shown) in the backing member to a fluid exhaust tube 58. Exhaust tube 58 is suitably connected through coupling 54 to exhaust tube 52, whereby a substantially continuous flow of coolant fluid may be supplied to and exhausted from conduit 46 in the heating ring.

Referring again to FIGS. 3 and 4, a pair of annular magnets 62, 64, each formed of a nonferrous material and having a substantially rectangular cross section, are seated in groove 26 in the hub. The magnets are positioned in the groove with one like set of their poles facing each other and their other like set of poles facing outwardly and away from each other; i.e., the north poles of the magnets may be on the sides of the magnet touching each other as shown in FIG. 4, and the south poles of the magnets may be on the outer sides which engage opposite sides of groove 26.

Underlying each of article-receiving pockets 34 in the ring is a cylindrical bore, such as that indicated at 68 in FIG. 3. The bore has substantially the same diameter as the article-receiving pocket and extends radially inwardly therefrom toward the center of the wheel through magnets 62, 64 and through the base of groove 26 into hub portion 22b of the backing member.

A cylindrical ceramic centering device 70 is secured in each of bores 68. Each centering device has a conical bore 72 opening outwardly toward the articlereceiving pocket and having sides which converge on extending toward the center of the heat wheel. A secondary bore 74 extends through the centering device from bore 72 toward the center of the wheel and is in direct communication with a right angle bore 76 in backing member 22. Bore 76 extends a distance toward the center of the wheel from device 70 and then makes a right angle turn to open to the back side of the heating wheel.

Referring again to FIG. 1, at 82 is indicated an elongated feed member for feeding pins 38, one at a time, into successive pockets 34 on the wheel as the wheel is rotated. As seen in FIG. 6, the member has a feed channel 84 extending longitudinally therealong which has a cross section adapted slidably to receive a single-file row of pins 38 held in proper orientation to be fed into the pockets on the wheel. The pins slide down the incline of the channel and the lower end of the channel rests atop the heating ring in such a position that as the ring is rotated in the direction of arrow 18 the forwardmost pin in the channel drops into a vacant pocket 34 as the ring passes under the channel. The incline of the channel and the spacing of the pockets on the heating wheel is such that only one pin will drop into each pocket. As a pin drops into a pocket it is guided by guide portion 34b of the pocket toward receiving portion 340. Magnets 62, 64 draw the pin downwardly and into the ceramic centering device 70, whereby one of its hubs enters conical bore 72, which centers and positions the pin in the wheel. With a pin in position in a pocket, as seen in FIG. 3 its rim 38a is closely encircled by receiving portion 34a.

Supported adjacent ring 30 of the heating wheel is an inductive heating coil 86. The coil constructed of electrically conductive hollow tubing, such as copper, and is connected to a suitable source of energy, such as a conventional high frequency source. Such source preferably would be adjustable to control the amount of inductive heating produced by the coil. Further, with the coil being constructed of hollow tubing, a coolant fluid may be passed therethrough to cool the coil during operation. The coil should have such rigidity that it supports itself, as shown in FIG. 3, out of contact with, but closely adjacent that portion of ring 30 which projects outwardly from backing member 22.

Referring specifically to FIG. 4, with coil 86 energized, each article-receiving pocket 34 and its associated slots 40, 42, form a separate closed loop coil and carry a resonating current around the rim of a pin in the pocket as they pass adjacent coil 86, causing the periphery of the rim of the pin to be heated rapidly. Slot 42 is made as narrow as possible so that the inductive current will be carried substantially entirely about the periphery of the rim of the pin. If a wide slot were to be provided at 42, what is referred to as a shadow effect would occur in the region of the slot, with the region of the rim of the pin adjacent the slot being heated less thoroughly than is the remainder of the rim.

Referring to FIGS. 1 and 5, a photocell 90 is mounted adjacent heating wheel 16. The sensing surface of the photocell is directed at the region through which a pin will pass as it is heated by the inductive coil. The photocell preferably should be one which is highly sensitive to radiation in the red and infrared portion of the spectrum. Such a photocell will be capable of detecting variations in radiation emitted by a pin due to tempera ture changes in a pin as it is heated. A photocell which has been found to work well is a Clairex CL 603/2. This photocell is a dual unit wired with both of its elements in series. This produces a very high dark-to-light resistance change resulting in high sensitivity to temperature variations in articles monitored by the photocell.

In FIGS. 3, 4 and 5, an air eject head 94 is illustrated mounted adjacent the back of the heating wheel. Head 94 is mounted on housing 12 by a pin which is slid ably received in a bore in the housing. A compression spring 102 intermediate housing 12 and head 94 biases the head into tight contact with the back of backing member 22. Head 94 has an elongated opening 104 on its side facing the heating wheel. The opening is positioned to communicate with each bore 76 in the backing member as it is rotated past the head in the region of the inductive heating coil. Referring to FIGS. 3 and 5, opening 104 is connected through a tube 106 and a normally-closed valve 108 to a supply of air under pressure I10.

When valve 108 is opened a stream of air under pressure from supply 110 is directed through tube 106 and opening 104 to a bore 76 in the backing member which communicates with opening 104 at that time. Such stream of air directed through a bore 76 is sufficient to dislodge a pin held in the pocket associated with that bore to allow it to drop into a quenching medium, or

coolant fluid, held in a tank 114, shown in FIG. 1, below the wheel.

Referring to FIG. 5, photocell 90 is connected through a circuit 116 to a solenoid 118. Solenoid 118, in turn, is operatively connected to valve 108, whereby actuation of the solenoid opens the valve.

Describing circuit 116, it includes a pair of input terminals 122, 124, which are connected to a source of alternating current through a double-pole, double-throw switch 126. Solenoid 118 has a pair of input teminals E, F. Input terminal 124 is connected directly to terminal F of the solenoid.

The circuit includes two silicon controlled rectiflers 130, 132, referred to herein as SCRs, each of which has an anode A, a cathode C, and a gate G. The circuit also includes a potentiometer 134.

Referring now to SCR 130, its cathode C is connected through a conductor 136 to input terminal 122. Its gate G is connected through a conductor 138 to a terminal of photocell 90, and its anode is connected to terminal E of solenoid 118. The anode of SCR 132 is connected to conductor 136, and thus to input terminal 122. Its cathode is connected to input E of the solenoid, and its gate is connected through potentiometer 134 to the other terminal of photocell 90.

Explaining the operation of circuit 116, with switch 126 closed, SCRs 130, 132 form a solid state switch in series with solenoid 118, and until such SCRs are turned on, they prevent current from flowing through the solenoid. The SCRs are turned on by lowering the resistance between their two gates. As has been explained previously, photocell 90 exhibits a high dark resistance and a rapid lowering of resistance when exposed to radiation in the red and infrared region. Thus, when photocell 90 is exposed to an increase in infrared radiation from a pin as the pin is heated, the resistance of the photocell decreases. When the combined resistance of the photocell and potentiometer 134 are lowered to a preselected level, the SCRs will be turned on. The point at which this occurs can be adjusted by adjusting the potentiometer whereby a preselected optimum temperature for a pin is heated by the apparatus will trigger the circuit.

When SCRs 130,132 are turned on, solenoid 118 is energized to open valve 108. This permits a stream of air under pressure to be directed through head 94 to dislodge a heated pin from the heating wheel and drop the pin into a quenching medium. After the heated pin has been ejected, the resistance in the photocell raises, returning the SCRs to their off states, deenergizing solenoid 18 and closing valve 108.

If a pin does not reach the preselected temperature prior to passing out of the heating region, it will remain in its pocket in the wheel until it is over a second tank 116. When it reaches a position over tank 116 a second air eject head (not shown) which is constantly blowing a jet of air through bores 76 moved therepast, automatically blows such a pin (which may be referred to as a reject) from the pocket and drops it into tank 116.

Operation of the apparatus will now be summarized. Pins to be heated are fed by channel 82 into successive pockets 34 on the heating wheel as the wheel is rotated under power. The pins are held in the wheel by the magnets adjacent the pockets. Continuous rotation of the wheel moves the pins in succession into a region adjacent energized inductive coil 86. While the pins are moved through a region adjacent the coil they are heated one after the other to a preselected temperature. When a pin is properly heated its temperature is detected by photocell which causes solenoid 118 to open valve 108 and direct a jet of air against the pin to dislodge it from the heating wheel and drop it into a tank of quenching fluid. Should the pin not reach the preselected temperature while in the heating region, it passes into a region above reject tank 116, where a continuously-operating air eject mechanism blows the pin out of the heating wheel and drops it into tank 116.

Referring to FIG. 2, modified apparatus for feeding pins to the heating wheel is indicated generally at 120. in this embodiment, heating wheel 16 is mounted on housing 12 with a spur gear 122 secured to the driving shaft for the wheel. A feed wheel 124, having the same diameter as the outer diameter of the ring 50 of the heating wheel, is mounted on a shaft to which is keyed a second spur 126 gear which meshes with gear 122. Gear 126 has a diameter similar to gear 122. Feed wheel 124 has a plurality of pockets 130 disposed about its periphery which open both to the near face and to the periphery of the wheel. The pockets are so formed that a pin may be slipped into the pockets from the near side of the wheel and may exit freely from the periphery of the wheel. The number of pockets on the feed wheel is equal to the number of pockets on the heating wheel, and the spacing of pockets 130 is similar to the spacing of the pockets on the heating wheel. A feed channel 132 is operable to feed successive pins, one after the other, into pockets 130 of the feed wheel as such is rotated in the direction of arrow 134.

An arcuate retainer member 136 is shaped to enclose the periphery of the feed wheel from a region adjacent feed channel 132 to a position where the bottom of feed wheel 124 is closely adjacent heating wheel 16. Retainer 136 is substantially L-shaped when viewed in cross section and acts to hold pins in pockets 130 as they are rotated with the feed wheel toward the heating wheel. The rotation of feed wheel 124 is synchronized with the rotation of heating wheel 16 by the engagement of spur gears 122, 124, whereby each pocket 130 as it passes under the bottom of the wheel is directly aligned with a pocket on wheel 16 and is adapted to deposit a pin therein.

From the foregoing it should be apparent that the apparatus of the invention is operable to provide continuous and rapid heat-treating of articles. Further, such is operable to produce close temperature control and low rejection rates in operation, due to the fact that the temperature of each individual part is checked as it is heated and such is ejected into a quenching medium only when it has reached its preselected temperature. Should a rivet not reach such preselected temperature it is automatically directed to a reject area.

With such apparatus the inductive heating coil may be operated continuously and the heating wheel for moving parts past the coil may be operated continuously and at a substantially set rate. There is no need to provide for intermittent operation of either of these elements.

While a preferred embodiment of the invention has been described herein, it should be apparent to those skilled in the art that variations and modifications are possible without departing from the spirit ,of the invention.

I claim:

1. Apparatus for heat treating articles comprising conveyor means for releasably holding a plurality of articles and conveying such articles in succession along a path,

continuously operating heating means adjacent said path for heating articles conveyed therealong in a zone through which said path extends,

sensing means operable to detect the temperature of discrete articles heated by said heating means while such are moving in said zone, and

ejecting means operatively connected to and controlled by said sensing means operable to eject an article from said conveyor and out of said zone when said sensing means detects that such article has been heated to a preselected temperature.

2. The apparatus of claim 1, wherein said sensing means comprises a photocell responsive to variations in radiation emitted by an article as it is heated.

3. The apparatus of claim 2, wherein said ejecting means comprises a supply of fluid under pressure, conduit means for directing a stream of such fluid against an article held by said conveyor means to dislodge the same and divert it from said path, and a normallyclosed valve in said conduit means inhibiting fluid flow to said conveyor means, and which further comprises means operatively connecting said photocell and said valve operable to open said valve when said photocell detects an article heated to a preselected temperature.

4. The apparatus of claim 1, wherein said heating means comprises an inductive heater and said ejecting means comprises means for selectively directing a stream of gas against an article while such is under the influence of said heater to dislodge the same from the conveyor means.

5. The apparatus of claim 1, wherein said conveyor means comprises an electrically conductive element and means for producing powered movement of said element, said element having an article-receiving pocket formed therein and a nonferrous magnet disposed adjacent said article-receiving pocket for holding an article therein, and said heating means comprises an inductive coil disposed adjacent a path along which said pocket travels on movement of the element.

6. The apparatus of claim 5, wherein said conveyor means further comprises nonconductive centering means for centering an article in said pocket.

7. The apparatus of claim 1, wherein said conveyor means comprises a power-driven ring element having article-receiving pockets disposed circumferentially thereabout, and a pair of magnets mounted adjacent a pocket for releasably holding an article therein, said magnets being positioned on opposite sides of the pocket with like poles of the magnets facing each other.

8. Apparatus for heat treating articles comprising inductive heating means,

conductive means adjacent said heating means for releasably holding an article and providing an electrical path thereabout during the inductive heating process,

sensing means operable to sense the temperature of an article held by said conductor means during the heating process,

ejecting means for ejecting the article from said conductive means during the heating process, and means operating said ejecting means controlled by said sensing means.

9. The apparatus of claim 8, wherein said conductive means is part of a moving conveyor and the conductive means is movable with conveyor movement recurrently past said inductive heating means, and said ejecting means is operable to eject an article from said conductive means during movement of said conductive means.

10. Apparatus for heat treating articles comprising a power-driven ring element having a pluarlity of article-receiving pockets spaced circumferentially thereabout for receiving and holding articles therein,

means for rotating said ring about its central axis for conveying articles held in said pockets successively along a path,

feeder means for supplying articles to successive pockets on the ring,

continuously operating inductive heating means adjacent said ring element for heating articles moved therepast in a zone through which said path extends,

sensing means operable to detect the temperature of discrete articles heated by said heating while such are moving in said zone, and

ejecting means operatively connected to and controlled by said sensing means operable to eject an article from said ring element when said sensing means detects that the article has been heated to preselected temperature.

v =t t 8 t 

1. Apparatus for heat treating articles comprising conveyor means for releasably holding a plurality of articles and conveying such articles in succession along a path, continuously operating heating means adjacent said path for heating articles conveyed therealong in a zone through which said path extends, sensing means operable to detect the temperature of discrete articles heated by said heating means while such are moving in said zone, and ejecting means operatively connected to and controlled by said sensing means operable to eject an article from said conveyor and out of said zone when said sensing means detects that such article has been heated to a preselected temperature.
 2. The apparatus of claim 1, wherein said sensing means comprises a photocell responsive to variations in radiation emitted by an article as it is heated.
 3. The apparatus of claim 2, wherein said ejecting means comprises a supply of fluid under pressure, conduit means for directing a stream of such fluid against an article held by said conveyor means to dislodge the same and divert it from said path, and a normally-closed valve in said conduit means inhibiting fluid flow to said conveyor means, and which further comprises means operatively connecting said photocell and said valve operable to open said valve when said photocell detects an article heated to a preselected temperature.
 4. The apparatus of claim 1, wherein said heating means coMprises an inductive heater and said ejecting means comprises means for selectively directing a stream of gas against an article while such is under the influence of said heater to dislodge the same from the conveyor means.
 5. The apparatus of claim 1, wherein said conveyor means comprises an electrically conductive element and means for producing powered movement of said element, said element having an article-receiving pocket formed therein and a nonferrous magnet disposed adjacent said article-receiving pocket for holding an article therein, and said heating means comprises an inductive coil disposed adjacent a path along which said pocket travels on movement of the element.
 6. The apparatus of claim 5, wherein said conveyor means further comprises nonconductive centering means for centering an article in said pocket.
 7. The apparatus of claim 1, wherein said conveyor means comprises a power-driven ring element having article-receiving pockets disposed circumferentially thereabout, and a pair of magnets mounted adjacent a pocket for releasably holding an article therein, said magnets being positioned on opposite sides of the pocket with like poles of the magnets facing each other.
 8. Apparatus for heat treating articles comprising inductive heating means, conductive means adjacent said heating means for releasably holding an article and providing an electrical path thereabout during the inductive heating process, sensing means operable to sense the temperature of an article held by said conductor means during the heating process, ejecting means for ejecting the article from said conductive means during the heating process, and means operating said ejecting means controlled by said sensing means.
 9. The apparatus of claim 8, wherein said conductive means is part of a moving conveyor and the conductive means is movable with conveyor movement recurrently past said inductive heating means, and said ejecting means is operable to eject an article from said conductive means during movement of said conductive means.
 10. Apparatus for heat treating articles comprising a power-driven ring element having a pluarlity of article-receiving pockets spaced circumferentially thereabout for receiving and holding articles therein, means for rotating said ring about its central axis for conveying articles held in said pockets successively along a path, feeder means for supplying articles to successive pockets on the ring, continuously operating inductive heating means adjacent said ring element for heating articles moved therepast in a zone through which said path extends, sensing means operable to detect the temperature of discrete articles heated by said heating while such are moving in said zone, and ejecting means operatively connected to and controlled by said sensing means operable to eject an article from said ring element when said sensing means detects that the article has been heated to preselected temperature. 